Effects of Environmental and Water Quality Variables on Histamine-Producing Bacteria Concentration and Species in the Northern Gulf of Mexico

Scombrotoxin (histamine) fish poisoning is a common seafood-borne illness attributed to toxin production by histamine-producing bacteria (HPB) in fish tissues during decomposition. In laboratory studies, growth of HPB and other bacterial species is affected by physical and chemical attributes, but natural communities of HPB are not well understood. To determine how in situ environmental and water quality variables may affect density of HPB in the natural aquatic environment, we compared presence and abundance of HPB to ambient temperature, salinity, dissolved oxygen, fecal coliforms, male-specific coliphage, nutrient concentrations, carbon and nitrogen stable isotope ratios, and C:N in water samples collected from July 2017 to February 2018 along a natural salinity gradient in a tidal river on the coast of northern Gulf of Mexico. HPB in water samples were quantified using a real-time PCR, most probable number method. HPB species were identified via 16S rRNA gene sequences. Temperature and salinity were determined to be the main factors driving HPB presence and concentration. Canonical correspondence analysis revealed that different HPB were associated with different environmental conditions. Photobacterium damselae was found under warmer, higher-salinity conditions; Raoultella planticola was found at colder, lower-salinity conditions; Enterobacter aerogenes was found at warmer, lower-salinity conditions; and Morganella morganii was found at most sites, independent of environmental conditions. These results showed that naturally occurring HPB abundance and species composition can be affected by environmental conditions, which could manifest in various potentials for histamine formation and scombrotoxin fish poisoning risk based on environmental factors. IMPORTANCE This study determined the effects of environmental conditions on presence and abundance of naturally occurring histamine-producing bacteria in the northern Gulf of Mexico. Here, we show that HPB abundance and species composition are related to in situ ambient temperature and salinity, with the magnitude of this effect dependent on the particular HPB species. This finding suggests that environmental conditions at fishing sites could affect the risk of human illness from scombrotoxin (histamine) fish poisoning.

Genomic Complexity Predicts Resistance to Endocrine Therapy and CDK4/6 Inhibition in Hormone Receptor-Positive (HR+)/HER2-Negative Metastatic Breast Cancer

PURPOSE

Clinical biomarkers to identify patients unlikely to benefit from CDK4/6 inhibition (CDK4/6i) in combination with endocrine therapy (ET) are lacking. We implemented a comprehensive circulating tumor DNA (ctDNA) analysis to identify genomic features for predicting and monitoring treatment resistance.

EXPERIMENTAL DESIGN

ctDNA was isolated from 216 plasma samples collected from 51 patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) metastatic breast cancer (MBC) on a phase II trial of palbociclib combined with letrozole or fulvestrant (NCT03007979). Boosted whole-exome sequencing (WES) was performed at baseline and clinical progression to evaluate genomic alterations, mutational signatures, and blood tumor mutational burden (bTMB). Low-pass whole-genome sequencing was performed at baseline and serial timepoints to assess blood copy-number burden (bCNB).

RESULTS

High bTMB and bCNB were associated with lack of clinical benefit and significantly shorter progression-free survival (PFS) compared with patients with low bTMB or low bCNB (all P < 0.05). Dominant APOBEC signatures were detected at baseline exclusively in cases with high bTMB (5/13, 38.5%) versus low bTMB (0/37, 0%; P = 0.0006). Alterations in ESR1 were enriched in samples with high bTMB (P = 0.0005). There was a high correlation between bTMB determined by WES and bTMB determined using a 600-gene panel (R = 0.98). During serial monitoring, an increase in bCNB score preceded radiographic progression in 12 of 18 (66.7%) patients.

CONCLUSIONS

Genomic complexity detected by noninvasive profiling of bTMB and bCNB predicted poor outcomes in patients treated with ET and CDK4/6i and identified early disease progression before imaging. Novel treatment strategies including immunotherapy-based combinations should be investigated in this population.

Abstract OT3-11-01: TK IMPACT: Treatment Monitoring of Hormone Receptor Positive (HR+), HER2 Negative (HER2-) Metastatic Breast Cancer (MBC) Patients Receiving CDK 4/6 Inhibitors (CDK4/6i) with DiviTum® Thymidine Kinase 1 Activity

Background: CDK 4/6i have altered the therapeutic landscape of HR+, HER2- MBC, improving progression free and overall survival (PFS and OS) compared to endocrine therapy (ET) alone. Despite durable responses to CDK 4/6i in a large majority of patients, treatment response monitoring in this population has historically included numerous serial blood-based and imaging studies at frequent time points. There is a growing global interest in utilizing novel non-invasive biomarker-driven disease monitoring assessments to improve patient outcomes and reduce health care costs. Thymidine kinase 1 (TK1), a key cell-cycle regulated enzyme important for nucleotide metabolism during DNA synthesis, is regulated by the E2F pathway, downstream of CDK 4/6. Studies have shown that DiviTum® TK1 activity (TKa) may serve as both a prognostic and predictive biomarker of CDK 4/6i treatment response (McCartney et al, Clin Canc Res, 2020; Malorni et al, Eur J Cancer, 2022; Bagegni et al, Breast Cancer Res, 2017). Early TKa suppression within 2 weeks (wk) post CDK 4/6i therapy initiation is associated with improved PFS, suggesting a subgroup of patients who may be able to de-escalate imaging frequency. Elevated TKa at baseline and post CDK 4/6i may identify patients with CDK 4/6i-resistant disease and disease progression (PD) requiring early therapy modification. TK IMPACT is a prospective, single-arm trial designed to assess the impact of incorporation of DiviTum® TKa on a physician’s decision regarding subsequent timing of routine disease monitoring modalities in patients with advanced HR+, HER2- MBC receiving ET plus CDK 4/6i (NCT04968964). Methods: Blood sample collections will be analyzed using DiviTum® TKa at baseline (bl), wk 2, 4, 6, 8, and Q 4 wks thereafter beginning at wk 8 during the first 24-wk time period of study enrollment (+/- 3 days); followed by Q 12 wks thereafter, until PD or 36 months, whichever occurs first. Optional repeat TKa within 2-4 wks (+/-3 days) is permitted in case of rising TKa. Research blood (bl, wk 2, 12, 24, 48, and PD) and optional archival tumor tissue collection at diagnosis and PD will be obtained for correlatives. The investigator will record intended imaging modalities and timing prior to receipt of TKa, followed by documentation of any changes in imaging testing interval after receipt of TKa. Key eligibility criteria include postmenopausal women age ≥18 years with HR+, HER2- MBC, to initiate (Cohort 1) or are currently receiving (≤24 months, Cohort 2) any FDA approved first line ET plus CDK 4/6i with a life expectancy &gt; 6 months. The primary endpoint is any physician-reported intended change in imaging testing interval post TKa by study cohort, within the first 48-wk period of study participation. Key secondary endpoints are concordance rate between TKa values and progression status at first on-study imaging and longitudinal TKa dynamics. Key exploratory endpoints include plasma and tumor tissue-based biomarkers of CDK 4/6i response and resistance. A total of 40 patients will be enrolled (n=20/Cohort). The expected change rate is 20% with a 95% Wilson confidence interval of 0.105~0.248 across all patients and if within each cohort, with a 95% Wilson confidence interval of 0.081~0.416 for N=20. N=40 allows the lower limit of the 95% CI &gt; 10% and that of the N=20 in Cohort 1 to be ~10%, indicating some clinically meaningful influence of TKa progression on patient management. The study is open to accrual and has presently enrolled 5 patients.

Citation Format: Nusayba A. Bagegni, Isabella Grigsby, Leslie Nehring, Jingqin Luo, Jennifer Powers Carson, David W. Gibson, Meghan Horvath, Katherine K. Clifton, Foluso O. Ademuyiwa, Rama Suresh, Ashley Frith, Andrew A. Davis, Lindsay L. Peterson, Ron Bose, Amy Williams, Mattias Bergqvist, Cynthia Ma. TK IMPACT: Treatment Monitoring of Hormone Receptor Positive (HR+), HER2 Negative (HER2-) Metastatic Breast Cancer (MBC) Patients Receiving CDK 4/6 Inhibitors (CDK4/6i) with DiviTum® Thymidine Kinase 1 Activity [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-11-01.

Abstract P3-06-06: Real-world analysis of adverse events of patients with triple negative breast cancer receiving therapy per KEYNOTE-522

Background: KEYNOTE-522 was a randomized, double-blind, placebo-controlled phase 3 trial which resulted in the FDA approval of pembrolizumab with neoadjuvant chemotherapy for patients (pts) with newly diagnosed, high-risk, early-stage triple negative breast cancer (TNBC). Given the improvement in pathological complete response (pCR) and event-free survival rates, this regimen has emerged as standard-of-care (SOC) therapy. Adverse events in pts on this treatment regimen in clinical practice is unknown and understanding the real-world toxicity of this regimen is critical.

Methods: In this IRB approved retrospective, single-center study we examined pts with early-stage TNBC who received planned treatment per KEYNOTE-522 per SOC from 2021-present. This regimen includes a year of pembrolizumab combined with 4 cycles of neoadjuvant carboplatin/paclitaxel followed by 4 cycles of doxorubicin/cyclophosphamide. Number and length of treatment delays, treatment related toxicities of all grades, and pCR rate were collected from the electronic medical record.

Results: Of the 87 identified pts, 2 were excluded due to locally recurrent or metastatic disease and 6 did not receive immunotherapy due to concerns for toxicity or patient preference. Of the 79 pts who initiated treatment with chemotherapy and immunotherapy, median age of the cohort was 52 (27-77). 9 pts had a BRCA1 mutation and 1 pt had a BRCA2 mutation. 41 (51.9%) had T1-2 disease and 38 (48.1%) had T3-4 disease. 37 (46.8%) pts had N0 disease and 42 (53.2%) had N1-3 disease. 15 pts had baseline comorbidities, including heart disease, kidney disease, type II DM, and/or peripheral neuropathy. 68 pts (86.1%) had baseline ECOG 0, 9 (11.4%) had ECOG 1, and 2 (2.5%) had ECOG 2. At the time of analysis, 70 pts (88.6%) were receiving active treatment, of which 47 (67.1%) had completed ≥50% of the planned neoadjuvant therapy. Of pts completing ≥50% of planned neoadjuvant therapy and pts off therapy (N=56), 31 (55.4%) had 1 or more hospitalizations and 23 (41.1%) had 1 or more emergency room visits. 30 pts had treatment delays (53.6%) and 21 pts (37.5%) had dose reductions. Rates of adverse events are presented in Table 1. Of the 79 analyzed pts, 35 have undergone surgery. pCR rate was 45.7% (N=16). 8 (22.9%) pts had RCB-I, 4 (11.4%) pts had RCB-II, 3 (8.6%) pts had RCB-III, and 4 (11.4%) pts had residual disease without RCB calculation. Updated analysis will be included at time of presentation.

Conclusions: In this single-center retrospective study of pts receiving chemoimmunotherapy for TNBC, we found higher rates of grade 3 toxicity, including nausea, fatigue, neutropenia, diarrhea, peripheral neuropathy, and hypothyroidism, and lower pCR rate than was reported in the KEYNOTE-522 trial. This may reflect a more heterogeneous population of pts treated in routine clinical practice who are typically less fit than pts on clinical trials. Additionally, pts in this study had higher T stages (48.1% with T3-4 disease vs 26.0% in trial) and node positive disease (53.7% with N1-3 disease vs 48.8% in trial). Limitations include immaturity of data and small sample size; however, these data warrant validation through longer-term follow-up and multicenter validation.

Adverse Events in pts receiving Keynote-522 regimen as SOC and on clinical trial

Citation Format: Mara Hofherr, Jennifer Hedgecorth, Foluso O. Ademuyiwa, Lindsay L. Peterson, Nusayba A. Bagegni, Rama Suresh, Ashley Frith, Ron Bose, Katherine Weilbaecher, Cynthia Ma, Andrew A. Davis, Katherine K. Clifton. Real-world analysis of adverse events of patients with triple negative breast cancer receiving therapy per KEYNOTE-522 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-06-06.

Abstract PD13-09: PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors

Background: CDK4/6 inhibitors (CDK4/6i) paired with endocrine therapy (ET) are considered first-line (1L) therapy for patients (pts) with HR+ HER2- advanced breast cancer (aBC). A minority of pts will demonstrate primary resistance to CDK4/6i, as characterized by early progression. Thymidine kinase 1 (TK1) is a cell-cycle regulated enzyme downstream of CDK4/6 and involved in nucleotide metabolism during DNA synthesis. Prior studies have shown TK1 may serve as a biomarker of response to CDK4/6i, with early TK1 activity (TK1a) suppression after initiation of CDK 4/6i therapy associated with improved PFS. Lack of TK1a suppression may be associated with primary resistance to CDK4/6i. In this study, we aim to analyze response to subsequent lines of therapy and overall survival (OS) of pts with early progression on 1L CDK4/6i. Methods: Pts with HR+ HER2- aBC from a phase II trial of an alternative schedule of palbociclib (palbo alt dosing trial NCT 3007979) and from a retrospective palbociclib study were included in this analysis. Pts in the palbo alt dosing trial underwent baseline and C1D15 TK1a analysis after initiation on CDK4/6i. C1D15 TK1a suppression was defined at TK1a &lt; 30 Du/L. Pts in the retrospective palbociclib study included pts receiving palbo as part of their standard of care 1L therapy for HR+ HER2- aBC at Washington University in Saint Louis from 2016 to 2021. Clinical information, including treatment start and stop dates on each of the next-line therapies, were collected from the electronic medical record. PFS was estimated by the treatment duration on a specified treatment regimen. Early progression on CDK4/6i was defined as PFS &lt; 6 mo. Best response was defined as next line of therapy with the numerically longest PFS. OS was defined as time to death from the initiation of CDK4/6i. Results: Of the 54 pts enrolled on the palbo alt dosing trial, 51 pts were evaluable for clinical benefit and 46 pts were evaluable for TK1a suppression rate at C1D15. 7 pts (15.2%) were found without TK1a suppression at C1D15. This lack of TK1a suppression on palbo was associated with a significantly shorter PFS (median PFS=3.1 mo) compared to not reached in pts with TK1a suppression at C1D15. We conducted clinical analysis on N=26 pts who exhibited early progression on CDK4/6i which included 10 pts from the palbo alt dosing trial and 16 from the retrospective study. The average subsequent line of therapies in this cohort was 3, with the most common second line (2L) therapy being chemotherapy (N=17, 65.4%) and ET (N=8, 30.8%). The median PFS for pts receiving 2L chemotherapy and ET was 4.09 mo and 3.64 mo, respectively. 10 pts received both chemotherapy and ET with 7 (70.0%) achieving best response with chemotherapy compared to 3 pts (30.0%) who achieved best response with ET. The median OS for the cohort was 14.6 mo. Conclusions: Early progression on CDK4/6i is associated with a particularly poor prognosis. In our cohort, the median OS was far below the expected median OS for pts receiving 1L palbo as reported in the PALOMA-2 trial (14.6 mo vs 53.9 mo). Early progression on CDK4/6i is associated with more aggressive disease which may respond more favorably to chemotherapy, as demonstrated by best response to therapy. Further prospective studies are warranted to explore this treatment approach.

Citation Format: Katherine K. Clifton, Shana N. Thomas, Jingqin Luo, Jing Xi, Nusayba A. Bagegni, Foluso O. Ademuyiwa, Rama Suresh, Ashley Frith, Andrew A. Davis, Ron Bose, Katherine Weilbaecher, Whitney L. Hensing, Timothy Pluard, Massimo Cristofanilli, Hyo S. Han, Adam M. Brufsky, Kevin Kalinsky, Shom Goel, Seth A. Wander, Lindsay L. Peterson, Cynthia Ma. PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD13-09.

A phase II study of palbociclib plus letrozole plus trastuzumab as neoadjuvant treatment for clinical stages II and III ER+ HER2+ breast cancer (PALTAN)

Patients with ER+/HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after chemotherapy with dual HER2 blockade than ER-/HER2+ BC. Endocrine therapy plus trastuzumab is effective in advanced ER+/HER2+ BC. Inhibition of CDK4/6 and HER2 results in synergistic cell proliferation reduction. We combined palbociclib, letrozole, and trastuzumab (PLT) as a chemotherapy-sparing regimen. We evaluated neoadjuvant PLT in early ER+/HER2+ BC. Primary endpoint was pCR after 16 weeks. Research biopsies were performed for whole exome and RNA sequencing, PAM50 subtyping, and Ki67 assessment for complete cell cycle arrest (CCCA: Ki67 ≤ 2.7%). After 26 patients, accrual stopped due to futility. pCR (residual cancer burden-RCB 0) was 7.7%, RCB 0/I was 38.5%. Grade (G) 3/4 treatment-emergent adverse events occurred in 19. Among these, G3/4 neutropenia was 50%, hypertension 26.9%, and leucopenia 7.7%. Analysis indicated CCCA in 85% at C1 day 15 (C1D15), compared to 27% at surgery after palbociclib was discontinued. Baseline PAM50 subtyping identified 31.2% HER2-E, 43.8% Luminal B, and 25% Luminal A. 161 genes were differentially expressed comparing C1D15 to baseline. MKI67, TK1, CCNB1, AURKB, and PLK1 were among the genes downregulated, consistent with CCCA at C1D15. Molecular Signatures Database gene-sets analyses demonstrated downregulated processes involved in proliferation, ER and mTORC1 signaling, and DNA damage repair at C1D15, consistent with the study drug's mechanisms of action. Neoadjuvant PLT showed a pCR of 7.7% and an RCB 0/I rate of 38.5%. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments. ClinicalTrials.gov- NCT02907918.

Abstract P2-13-01: Phase 2 study of neoadjuvant palbociclib, letrozole, and trastuzumab in patients with ER+ HER2+ breast cancer (PALTAN)

Background Patients (pts) with ER+ HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after neoadjuvant chemotherapy with dual HER2 blockade than pts with ER- HER2+ BC. Endocrine therapy (ET) plus trastuzumab is effective in advanced ER+ HER2+ BC, but pCR rate is low in the neoadjuvant setting. Inhibition of CDK4/6 and HER2 results in synergistic reduction in cell proliferation in preclinical studies. We therefore combined ET with CDK4/6 inhibition and trastuzumab in ER+ HER2+ BC as a chemotherapy-sparing regimen. Methods We evaluated the efficacy of palbociclib, letrozole, trastuzumab (PLT) in the neoadjuvant setting for pts with stages II or III ER+ HER2+ BC. Primary endpoint was pCR after 16 weeks of therapy. We assumed null of 15% pCR and pCR ≥ 30% warrants further investigation. To achieve 80% power at 1-sided 0.05 significance, 48 pts were to be enrolled. Evaluable population included pts who completed Cycle (C) 1 unless discontinued due to treatment-emergent adverse events (TEAEs) prior to completing C1. All who received one dose on study were considered evaluable for toxicity. Biopsies were collected at baseline (BL), C1 day 15 (C1D15), and surgery for RNA sequencing and central Ki67 assessment, for PAM50 subtype distribution, complete cell cycle arrest (CCCA: Ki67 ≤2.7%) at C1D15 and surgery, and treatment induced signaling changes. Results Accrual stopped early due to futility. 26 pts accrued were evaluable for efficacy and toxicity. pCR (residual cancer burden- [RCB] 0) was 7.7% (95% CI 0.9 - 25.1%) and RCB 0/I was 38.5% (95% CI 20.2 - 59.4%). TEAEs (n= 337) were seen in all pts (71.5% grade [G] 1, 19.3% G2, 8.6% G3, 0.6% G4); the most common were leukopenia (7.7%), neutropenia (7.1%), anemia (5.9%). G3/4 TEAEs occurred in 19 pts (73.1%). Among the 19, incidence of G3/4 neutropenia was 50%, hypertension 26.9%, leucopenia 7.7%. TEAEs (hypertension, ventricular tachycardia, pulmonary edema) leading to treatment discontinuation were reported in 1 pt. Two pts had at least one SAE. No treatment-related deaths occurred. Pt reported outcomes using NCI PRO-CTCAE revealed no differences in appetite, nausea, respiratory symptoms, edema, palpitations, rashes and dry skin, or concentration from BL to end of C4. Pts had worsening hair loss from BL to end of C4. Ki67 analysis indicated CCCA in 78% at C1D15, compared to 18% at surgery after only P had been discontinued approximately 4 weeks prior to surgery. RNA sequencing was performed on available biopsies collected at BL (N=16), C1D15 (N=5), and surgery (N=2) from 16 pts. Among 16 BL samples, PAM50 subtyping identified 5 (31.3%) basal-like, 2 (12.5%) HER2-E, 6 (37.5%) Lum B, and 3 (18.8%) normal. Subtype switching to Lum A at C1D15 (N=3, 1 each with HER2-E, Lum B, and normal at BL) or normal (N=2, 1 basal and 1 HER2-E at BL) was observed. 161 genes were differentially expressed (FDR p&lt;0.05); 145 downregulated and 16 upregulated comparing C1D15 to BL. MKI67, TK1, CCNB1, AURKB, PLK1 were among the downregulated genes, consistent with CCCA for majority of the samples at C1D15 by Ki67. Analysis of the Molecular Signatures Database Hallmark gene-sets comparing C1D15 and BL samples demonstrated downregulated biological processes involved in proliferation (E2F targets, G2M checkpoint, MYC targets, mitotic spindle), signaling (Estrogen response, mTORC1 signaling), and DNA damage (DNA repair) at C1D15, consistent with the mechanisms of action of the study drugs. E2F targets were higher in BL samples of RCB II/III, compared to RCB I (FDR p=0.042). Conclusions PALTAN did not meet its primary endpoint of pCR. Neoadjuvant PLT showed a pCR of 7.7% but was well tolerated. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments, despite significant heterogeneity of intrinsic subtypes. Clinical trial information: NCT02907918.

Citation Format: Foluso O Ademuyiwa, Donald Northfelt, Tracey O'Connor, Ellis Levine, Jingqin Luo, Yu Tao, Jeremy Hoog, Marie Laury, Tracy Summa, Trish Hammerschmidt, Zhanfang Guo, Ashley Frith, Katherine Weilbaecher, Mateusz Opyrchal, Rebecca Aft, Katherine Clifton, Rama Suresh, Nusayba Bagegni, Ian S Hagemann, Cynthia X Ma. Phase 2 study of neoadjuvant palbociclib, letrozole, and trastuzumab in patients with ER+ HER2+ breast cancer (PALTAN) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-01.

Abstract PS2-09: Next generation sequencing (NGS) in older adults with breast cancer using tissue-based and circulating tumor DNA (ctDNA) assays

Background: With advances in next generation sequencing (NGS) and now approved targeted therapy in breast cancer, genomic testing to identify potentially actionable mutations has become a common practice in patients (pts) with advanced breast cancer using both ctDNA and traditional tissue-based assays. Less is known regarding physician practice patterns in obtaining NGS testing and the practical implications of testing in older adults with breast cancer.Methods: Pts with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360® or Tempus®) between 5/2015 and 5/2020 at Siteman Cancer Center. Pts with advanced breast cancer who underwent genomic profiling using a tissue-based NGS assay (Tempus®) between 12/2017 and 5/2020 at this institution were also included. Clinicopathological histories were obtained from the medical record. Correlations were examined using a Fisher’s exact test.Results: During 5/15-5/20, 244 pts underwent ctDNA testing and 147 pts had a tissue-based NGS assay performed. There was no significant difference between the number of pts ≥ 65 years-old who underwent ctDNA testing (n=78, 32.0%) and tissue testing (n=37, 25.2%). There was no statistically significant difference between date of metastatic diagnosis and date of NGS testing between the older and younger cohorts. In pts who underwent tissue-based NGS testing, there was no significant difference between site of tissue tested (distant recurrence vs local) in the older and younger cohorts. The most common clinical managements following both ctDNA and tissue-based testing are presented in Table 1. Out of the 391 pts who underwent testing, 27 pts had both ctDNA and tissue-based NGS performed. Pts ≥ 65 were less likely to have both assays performed (n=3, 11.1%; p&lt;0.05). In pts undergoing both assays, there were high concordance rates of ESR1 (81.5%) and PIK3CA (81.5%) mutations. Mean time between tissue and plasma collection for NGS testing in pts undergoing both assays was 356.4 days.

Conclusion: Older adults, who are typically less likely to be included in clinical trials, may still benefit from NGS to reveal potentially targetable mutations. It is reassuring in our cohort that older adults had ctDNA and tissue-based NGS performed at similar rates as part of standard of care treatment. The clinical management following NGS testing was also not significantly different in the older adult cohort. Older adults were less likely to have both tissue and ctDNA testing performed however, given the high concordance rates between tests, this may be less clinically relevant.

Table 1clinical management following NGS testing≥65 years-old&lt;65 years-oldp valueno actionable mutations41 (35.7%)123 (44.6%)p=0.1testing results saved for potential future use27 (23.5%)45 (16.3%)p=0.1change in management15 (13.0%)41 (14.9%)p=0.6

Citation Format: Katherine K Clifton, Jingqin Luo, Yu Tao, Jennifer Saam, Thereasa Rich, Timothy Rearden, Anna Roshal, Ashley Frith, Caron Rigden, Foluso Ademuyiwa, Katherine Weilbaecher, Leonel Hernandez Aya, Lindsay Peterson, Nusayba Bagegni, Rama Suresh, Ron Bose, Tanya Wildes, Mateusz Opyrchal, Cynthia Ma. Next generation sequencing (NGS) in older adults with breast cancer using tissue-based and circulating tumor DNA (ctDNA) assays [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-09.

Mutation profile differences in younger and older patients with advanced breast cancer using circulating tumor DNA (ctDNA)

PURPOSE

Little is known regarding the mutation profiles of ctDNA in the older adult breast cancer population. The objective of this study is to assess differences in mutation profiles in the older adult breast cancer population using a ctDNA assay as well as assess utilization of testing results.

METHODS

Patients with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360) between 5/2015 and 10/2019 at Siteman Cancer Center. The profiling results of a multi-institutional database of patients with advanced breast cancer who had undergone molecular profiling were obtained. Associations between mutations and age group (≥ 65 vs. < 65) were examined using a Fisher's exact test.

RESULTS

In the single-institutional cohort, 148 patients (69.2%) were < 65 years old and 66 patients (30.8%) ≥ 65 years old. ATM, BRAF, and PIK3CA mutations were found more frequently in older patients with ER + HER2- breast cancers (p < 0.01). In the multi-institutional cohort, 5367 (61.1%) were < 65 years old and 3417 (38.9%) ≥ 65 years old. ATM, PIK3CA, and TP53 mutations were more common in the older cohort (p < 0.0001) and MYC and GATA3 mutations were less common in the older cohort (p < 0.0001). CtDNA testing influenced next-line treatment management in 40 (19.8%) patients in the single-institutional cohort.

CONCLUSION

When controlling for subtype, results from a single institution were similar to the multi-institutional cohort showing that ATM and PIK3CA were more common in older adults. These data suggest there may be additional molecular differences in older adults with advanced breast cancers.

Abstract P2-16-03: Neoadjuvant treatment of triple negative breast cancer patients with docetaxel and carboplatin to assess anti-tumor activity

Background: Anthracycline- and taxane-based neoadjuvant chemotherapy (NAT) in triple negative breast cancer (TNBC) patients yields a pathological complete response (pCR) rate of approximately 45%. Anthracyclines can lead to long-term toxicities including congestive heart failure and leukemia. TNBC patients achieving pCR have excellent long-term outcomes irrespective of NAT regimen. This study was designed to evaluate the efficacy of a non-anthracycline NAT regimen with carboplatin and docetaxel in TNBC. Correlative studies include detecting and tracking plasma circulating tumor DNA (ctDNA) to determine if it will predict clinical outcomes, and whole exome sequencing (WES) on tissue samples to decipher the genomic architecture of those who achieve pCR versus those who do not. Methods: This is a joint analysis of two identical multicenter trials. Eligible patients with AJCC 7 clinical stages II and III TNBC received docetaxel 75mg/m2 and carboplatin AUC 6 every 3 weeks X 6 cycles. Following NAT, all patients underwent definitive surgery. The primary endpoint is pCR (no invasive tumor in the breast and axilla). Secondary objectives include evaluating ctDNA as a prognostic biomarker that may be used in identifying TNBC patients at a high risk of disease relapse, and evaluating differences in the genomic architecture between pCR and non-pCR patients. Patients have a research biopsy at baseline, cycle 1 day 3 (optional), and at definitive surgery for those with residual disease. Plasma for ctDNA is collected at baseline, cycle 1 day 3, at definitive surgery, and every 6 months for 5 years. Results: Between 2014 and 2019, 103 patients have been registered. Median age is 53 years (range 25-74), 27.2%: African-American, 77.7%: clinical stage II. Ninety-nine have completed NAT and have had surgery. In the intent to treat population, the preliminary pCR rate is 46.5% (95% CI 36.9% - 56.2%). Nine (8.7%) have developed recurrent disease, and 7 (6.8%) have died. Preliminary ctDNA results from 6 patients (4 non-pCR, 2 pCR) show that ctDNA is detectable in 67%. We identified 627 somatic variants by exome analysis. Of these, 10 variants overlapped with the Swift panel (Accel-Amplicon™ 56G Oncology Panel v2) used for ctDNA sequencing and variant detection. TP53 variants were identified in all 6 patients’ tumor tissue samples. At least one TP53 variant was identified in 4 patients’ baseline pre-chemotherapy ctDNA. Both pCR patients had either no detectable ctDNA TP53 mutations, or clearance of ctDNA following chemotherapy. Three non-PCR patients had persistent TP53 mutations in ctDNA during the treatment course. WES and ctDNA analysis on all patients is currently ongoing. Conclusions: We report a very encouraging pCR rate of 46.5% in TNBC patients with carboplatin and docetaxel NAT. This rate is similar to observed rates with anthracycline- and taxane-based NAT and may represent an option for treatment for TNBC patients. Correlative genomic and ctDNA studies are ongoing. Clinical trial information: NCT02124902 & NCT02547987.

Citation Format: FOLUSO O ADEMUYIWA, Mothaffar F Rimawi, Tracy Summa, Jingqin Luo, Tao Wang, Rama Suresh, Lindsay Peterson, Michael Naughton, Ashley Frith, Leonel Hernandez-Aya, Katherine Weilbaecher, Cynthia Ma, Aadel A Chaudhuri, Yang-Yang Feng, Zachary L Skidmore, Obi L Griffith, Malachi Griffith, Matthew Ellis. Neoadjuvant treatment of triple negative breast cancer patients with docetaxel and carboplatin to assess anti-tumor activity [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-16-03.

Abstract P1-19-13: A phase II trial assessing the safety of an alternative dosing schedule of palbociclib (palbo) in hormone receptor positive (HR+), HER2 negative (HER2-) metastatic breast cancer (MBC): Alt Dose Palbo

Introduction: Palbo is approved in combination with an aromatase inhibitor or fulvestrant (FUL) for the treatment of HR+ HER2- MBC. The incidence of grade (G) 3/4 neutropenia (ANC) approaching 66% has been observed in phase 3 trials of palbo. We hypothesize that an alternative schedule of palbo, 5 days on/2 days off every 7 days, reduces the severity of neutropenia, therefore allowing continued weekly dosing and less dose reduction and discontinuation. Methods: A single arm phase II study (Alt Dose Palbo) was conducted in patients (pts) with HR+ HER2- MBC who had ≤1 prior systemic therapy in the metastatic setting (NCT03007979). Pts were treated with palbo 125 mg daily on a 5 days on/2 days off every 7-day schedule, along with letrozole (LET) or FUL per treating physician. Goserelin was administered if premenopausal. The primary objective was to determine the rate of G3/4 ANC within the first 29 days of treatment. Secondary objectives included determining the rate of G3/4 ANC during all cycles, rate of palbo dose reduction/interruption/discontinuation, adverse event (AE) profile per CTCAE v5, progression free survival (PFS), objective response rate (ORR) and clinical benefit rate (CBR) by RECIST 1.1. The sample size of 47 was calculated to provide 90% power based on one-sample binomial exact test at a 5% alpha level to test the one-sided null hypothesis of G3/4 ANC rate &gt;62% versus the alternative of &lt;40%. If G3/4 ANC was not observed in 24 or more pts, this alternative dosing will be deemed to have a better toxicity profile than standard schedule. Results: Between July 2017 to June 2019, 48 pts were enrolled at 2 institutions. 3 pts withdrew/went off during cycle 1 unrelated to the study, leaving 45 pts (33 LET, 12 FUL) with a median age of 63 (range: 34-87) years and visceral metastases in 23 (51%). Prior (neo) adjuvant chemotherapy and endocrine therapy (ET) were received in 20 (44%) and 25 (56%) pts, respectively. Six (13%) had 1 prior ET in the metastatic setting. 19 (42%) had primary or secondary endocrine resistance defined according to the ESMO advanced breast cancer guideline prior to enrollment to the study. As of July 1, 2019, with a median follow up of 9.5 months, 28 (62%) pts are still receiving study drug. 42 pts were evaluable for toxicities. There were no G4 AEs. Nine (21%) and 15 (36%) pts experienced G3 ANC in cycle 1 (up to day 29), and all cycles, respectively. 33 pts in cycle 1 and 27 pts in all cycles, did not experience G3/4 ANC during all cycles, exceeding the predefined boundary for better tolerability of this schedule. Palbo was dose reduced in 10 (23.8%) pts. Two (4.8%) discontinued palbo due to AE (one with G3 ANC not recovering to G1 in 2 wks and the other died (G5 event) with acute subdural hematoma with concurrent G3 thrombocytopenia). The common treatment related AEs are shown in the Table 1. The ORR was 48% (2 CR, 10 PR, 95% Wilson CI: 30-66.5%) among 25 evaluable pts. The CBR (defined by CR or PR or stable disease for at least 24 wks) was 76.74% (33 of 43 evaluable pts, 95% Wilson CI: 62.3-86.9%). PFS has not been evaluated. Conclusion: The Alt Dose Palbo trial with palbo scheduled at 5 days on/2 days off every 7 days, with no weeks off therapy, met its primary endpoint with reduced G3/4 ANC. Survival data is not yet mature and will be updated at the presentation. However, preliminary efficacy data appears comparable to prior report. Encouraging data from this study should be confirmed in a randomized study.

Table 1C1 D1-29 AEG1G2G3TotalWBC decreased26%50%17%93%ANC decreased10%43%21%74%Anemia38%12%0%50%Fatigue29%0%0%29%Platelets decreased14%0%2%17%Nausea12%2%0%14%All cycle AEG1G2G3TotalWBC decreased19%50%26%95%ANC decreased5%40%36%81%Anemia50%21%2%74%Fatigue36%5%0%40%Nausea26%2%0%29%Platelets decreased24%0%2%26%Alopecia21%0%0%21%Mucositis19%0%0%19%Hot flashes17%2%0%19%Constipation14%0%0%14%Arthralgia12%2%0%14%AST elevated10%0%2%12%Anorexia12%0%0%12%ALT elevated7%0%5%12%

Citation Format: Jairam Krishnamurthy, Jingqin Luo, Foluso Ademuyiwa, Rama Suresh, Caron Rigden, Timothy Reardon, Katherine Weilbaecher, Ashley Frith, Anna Roshal, Pavan Tandra, Mathew Cherian, Tracy Summa, Shana Thomas, Leonel Hernandez-Aya, Lindsay Peterson, Cynthia Ma. A phase II trial assessing the safety of an alternative dosing schedule of palbociclib (palbo) in hormone receptor positive (HR+), HER2 negative (HER2-) metastatic breast cancer (MBC): Alt Dose Palbo [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-13.

Randomized controlled trial of high-dose versus standard-dose vitamin D3 for prevention of aromatase inhibitor-induced arthralgia

PURPOSE

Half of hormone receptor-positive (HR+) breast cancer patients will develop joint pain, termed aromatase inhibitor-induced arthralgia (AIA), while taking aromatase inhibitor therapy. Though there is no universally accepted effective treatment for AIA, there has been some evidence to support high-dose vitamin D as a treatment.

METHODS

We randomized post-menopausal women who were beginning adjuvant AI therapy to receive standard-dose vitamin D3 (800 IU daily for 52 weeks), or high-dose vitamin D3 (50,000 IU weekly for 12 weeks, followed by 2000 IU daily for 40 weeks). The primary end point was development of AIA. The trial was designed to enroll 184 patients. This futility analysis was performed after 93 patients were enrolled.

RESULTS

The high-dose vitamin D regimen was effective in raising serum vitamin D levels, but there was no significant difference in development of AIA between the two arms. In the high-dose arm, 25 patients (54%) developed AIA, compared to 27 patients (57%) in the standard-dose arm. The planned futility analysis was positive; thus, the study was terminated. Neither baseline vitamin D nor 12-week vitamin D level was predictive of AIA development.

CONCLUSION

Although vitamin D levels were increased in the high-dose arm, there was no significant signal for benefit of high-dose vitamin D supplementation for AIA prevention in this unblinded trial. This study, along with several others, implies that vitamin D likely does not play a significant role in AIA for the majority of patients.

Abstract OT1-01-05: Endocrine treatment alone as primary treatment for elderly patients with estrogen receptor positive good prognosis operable breast cancer: A single arm phase II, single institution study

Background: It is estimated that approximately 46,000 women age &gt;75 are diagnosed annually with breast cancer. Due to competing co-morbidities, there is wide variation in treatment recommendations which can lead to over- or under-treatment. Though surgery for breast cancer is considered low-morbidity, many elderly women given a choice, choose not to have surgery. Previous randomized trials comparing surgery with tamoxifen versus endocrine therapy alone in women age &gt;70 unselected for ER status demonstrated similar overall survival with poorer local control in the latter group. A new standard of care needs to be defined for elderly women with good prognosis ER+ tumors, since these women may benefit from endocrine therapy alone to treat their cancer without compromising local and distant control.

Hypothesis: We hypothesize that endocrine therapy alone provides adequate local and systemic control of breast cancer in a subpopulation of women age 70 or older with ER+ breast cancer and good prognostic characteristics.

Primary Objective

To correlate response to neoadjuvant endocrine treatment at 6 months with Oncotype DX Recurrence Score (RS) in women with early-stage ER+ breast cancer who are age &gt;70.

Secondary Objective

1. To determine the breast cancer-specific survival of women with early-stage ER+ breast cancer, age &gt;70, treated with endocrine therapy alone.

2. To determine the rate of overall survival of women with early-stage ER+ breast cancer, age &gt;70 treated with endocrine therapy alone.

Study Design: This is a prospective single arm phase II study. Patients with clinical stage I/II ER+ breast cancer, grade 1-2, Ki67&lt;30 or RS &lt;18 (performed on the diagnostic core biopsy) continue to be enrolled and followed for time to progression. A Kaplan-Meier model will be used to estimate the 5-year local progression rate. If the true 5-year progression rate is 10%, then 50 patients will provide power = .90 at a one-sided .05 significance level to demonstrate that the rate is less than 25.5%. Exploratory objectives include: evaluation of the molecular characteristics of breast cancers of responders versus non-responders, determine compliance with medications, evaluate cost-effectiveness, and quality of life.

Results: Between February 2017 and April 2018, 11 patients were enrolled into the study. Two patients could not tolerate endocrine therapy and received standard of care treatment. For the 9 patients on study, average tumor size was 1.7cm, average Ki67 was 15%, average RS was 14. All of the patients received an aromatase inhibitor. At 6 months, 71% of the patients had a partial response, 28% had stable disease. None of the patients developed progressive disease.

Conclusion: A new standard of care needs to be defined for women age &gt;70 with good prognosis ER+ tumors, since these women may benefit from endocrine therapy alone to treat their cancer without compromising local and distant control. We continue to enroll patients to determine the optimal tumor markers for identifying women who can be treated with PET only to control their cancer.

Citation Format: Aft R, Cherian M, Frith A, Suresh R, Glover-Collins K, Naughton M, Moon C, Conant L, Ma C. Endocrine treatment alone as primary treatment for elderly patients with estrogen receptor positive good prognosis operable breast cancer: A single arm phase II, single institution study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT1-01-05.

Abstract PD6-02: A randomized, controlled trial of high dose vs. standard dose vitamin D for aromatase inhibitor-induced arthralgia in breast cancer survivors

Background: Approximately half of women on aromatase inihbitor (AI) therapy develop AI-induced arthralgia (AIA), and many discontinue the medication because of this common side effect. While Vitamin D has been studied as a treatment for AIA, trial results have been conflicting thus far.

Patients and Methods: All subjects were post menopausal women who were beginning adjuvant AI therapy for stage I-III hormone receptor positive breast cancer. Patients were randomized 1:1 to receive standard dose vitamin D3 (800 IU daily for 52 weeks) or high dose vitamin D3 (50,000 IU weekly for 12 weeks, followed by 2000 IU daily for 40 weeks). All patients also took oral calcium 600 mg daily. The primary endpoint was development of AIA, as defined by pre-specified changes in the Health Assessment Questionnaire II (HAQ-II). Secondary endpoints include compliance with AI therapy, and correlation between grip strength and development of AIA. Exploratory endpoint was measurement of inflammatory cytokine reduction in each arm. The trial was designed to enroll 184 patients, but this futility analysis was performed after 93 patients were enrolled. The futility boundary for stopping the trial early was calculated as p = 0.47.

Results: All 93 patients (46 in the high dose arm, and 47 in the standard dose arm) enrolled in the study at the time of the interim analysis were evaluable. The HAQ-II was completed at 12 weeks in 76% on the high dose arm, and 68% in the standard dose arm. Subjects who did not complete the questionnaire were deemed as study failures (i.e. development of AIA was assumed). In the high dose arm, 25 patients (54%) developed AIA, compared to 27 patients (57%) in the standard dose arm. The one-tailed p value is 0.3818, and the Z-score is 0.3, yielding only a 38% conditional power that that study would find a significant difference between the two arms. Thus, the study was terminated early for futility. There was no significant difference between the two arms in adherence to AI therapy. The grip strength and inflammatory cytokine data are pending at this time. They will be ready by the time of the conference.

Conclusions: There was no significant signal for benefit of high dose vitamin D supplementation, as compared to standard dose vitamin D, for AIA prevention in post menopausal women taking adjuvant AI therapy. These results further characterize the role of Vitamin D in AIA, and they inform future clinical trials in this arena. Further research is necessary, as this remains an important cause of non-adherence to this highly effective therapy.

Citation Format: Niravath P, Wang T, Hilsenbeck SG, Lipscomb K, Pavlick A, Jiralerspong S, Nangia J, Ellis M, Ademuyiwa F, Cherian M, Frith A, Ma C, Park H, Rigden C, Suresh R, Osborne CK, Rimawi MF. A randomized, controlled trial of high dose vs. standard dose vitamin D for aromatase inhibitor-induced arthralgia in breast cancer survivors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD6-02.

Retrospective Analysis of Treatment Patterns and Effectiveness of Palbociclib and Subsequent Regimens in Metastatic Breast Cancer

Background: Cyclin-dependent kinase (CDK) 4/6 inhibitors are now the standard of care for hormone receptor-positive (HR+), HER2-negative (HER-) metastatic breast cancer (MBC). However, guidelines are lacking regarding their optimal sequencing with other available agents. This study examines physician practice patterns and treatment outcomes of palbociclib and subsequent therapies in a real-world setting. Methods: A retrospective chart review was conducted for consecutive patients with MBC who received palbociclib between February 2015 and August 2017 at the Alvin J. Siteman Cancer Center. Kaplan-Meier method was used to generate time-to-event curves and estimate median progression-free survival (mPFS). Log-rank test was used to compare differences. Results: A total of 200 patients, with a median age of 59.4 years and a follow-up of 19.5 months, were included. Palbociclib was most frequently combined with letrozole (73.5%), followed by fulvestrant (25%), anastrozole (1%), and tamoxifen (0.5%). Most patients received palbociclib in the endocrine-resistant setting (n=42, n=50, and n=108 in the first-, second-, and subsequent-line settings, respectively), and the fraction of patients receiving palbociclib as first- or second-line therapy increased in recent months (P=.0428). mPFS was 20.7, 12.8, and 4.0 months with palbociclib administered in the first-, second-, and subsequent-line settings, respectively (P<.0001). Incidences of grade 3/4 neutropenia (41.5%) and dose reductions (29%) were comparable to reports in the literature. Among patients whose disease progressed on palbociclib (n=104), the most frequent next-line treatment was capecitabine (n=21), followed by eribulin (n=16), nab-paclitaxel (n=15), and exemestane + everolimus (n=12). mPFS with hormone therapy alone or in combination with targeted agents (n=32) after first-, second-, and subsequent-line palbociclib was 17.0, 9.3, and 4.2 months, respectively (P=.04). mPFS with chemotherapy (n=70) was not reached, 4.7, and 4.1 months after first-, second-, and subsequent-line palbociclib, respectively (P=.56). Conclusions: Palbociclib is effective for HR+/HER2- MBC in real-world practice. Hormone therapy alone or in combination with targeted agents remains an effective option after palbociclib progression.

Abstract P5-21-30: Retrospective review of palbociclib (Pal) efficacy and benefit from subsequent treatments following Pal progression in patients (pts) with hormone receptor positive (HR+) and HER2 negative (HER2-) metastatic breast cancer (MBC)

Background

The cyclin-dependent kinase (CDK) 4/6 inhibitor Pal is approved for HR+ HER2- MBC. However, the optimal therapy following Pal progression is unknown. Therefore we conducted this retrospective study to review Pal efficacy and summarize the practice pattern and responses to subsequent treatments post Pal progression.

Methods

We performed a chart review of pts with HR+ HER2- MBC who began Pal treatment at Washington University Siteman Cancer Center between Feb 16, 2015 and July 13, 2016 and collected information on pts demographics, diagnosis, and treatment history. Duration of therapy was used to calculate the progression free survival (PFS) for each regimen. Treatment was considered first-line if administered without any prior systemic therapy or at least 1 year from completion of adjuvant hormonal therapy (HT). Treatments received after progression on 1st line therapy or upon relapse during or within 1 year from the completion of adjuvant HT were considered second-line regimens.

Statistical analyses were performed on SAS software, version 9.4. The Kaplan-Meier method was used to generate time-to-event curves, from which median PFS was calculated. A stratified log-rank test was used for all comparisons, and the P value derived from the comparison was reported.

Results

We completed a chart review for 81 pts (78 female and 3 male; 63 Caucasian, 14 African American, and 4 other races) with HR+ HER2- MBC (68 were ER+PR+, 13 were ER+PR-) who received Pal plus letrozole (n=65) or fulvestrant (n=15) or anastrozole (n=1), with a median age of 62.0 years (range 28.1 - 85.6) at the start of Pal.

The median follow up was 20.0 months (mos) (range 10.8 – 27.9). 25 pts were still on Pal treatment. The median PFS on Pal was 19.9 mos in the first-line setting (n=20), compared to 12.1 mos and 4.4 mos in the second-line (n=14) and subsequent lines (n=47), respectively (p=0.0287). Among the 54 pts who progressed on Pal, 38 moved on to the next treatment. 20 pts received chemotherapy and 16 pts received HT or a HT combination. 2 pts received fulvestrant plus Pal upon progression on letrozole plus Pal, and treatment was still ongoing at 4 mos and 7 mos of follow up, respectively. The most common treatments post Pal were single-agent capecitabine (Cape) (n=9) and the combination of exemestane (Exe) and everolimus (Eve) (n=8). The median PFS was 4.7 mos with Cape compared to 8.4 mos with Exe and Eve (p=0.60). The median PFS was 4.7 mos for the 20 pts who received chemo, whereas the median PFS was 4.9 mos with subsequent HT (n=16) (p=0.75).

Conclusion

Pal plus letrozole or fulvestrant is effective for the treatment of HR+ HER2- MBC, with activity observed beyond the 1st and 2nd line treatment settings. The PFS of Pal observed in this single center retrospective study is consistent with that of published data. Single-agent cape or the Exe and Eve combination were common treatment choices following progression on Pal. Although the study is limited by its small sample size, the median PFS of 8.4 mos with Exe and Eve indicates its potential efficacy in the setting of Pal progression. Additional pts and followup data will be presented.

Citation Format: Xi J, Oza A, Thomas S, Naughton M, Ademuyiwa F, Weilbaecher KN, Suresh R, Bose R, Cherian MA, Hernandez-Aya L, Frith A, Peterson LL, Krishnamurthy J, Ma CX. Retrospective review of palbociclib (Pal) efficacy and benefit from subsequent treatments following Pal progression in patients (pts) with hormone receptor positive (HR+) and HER2 negative (HER2-) metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-30.

Incidence of migraine relative to menstrual cycle phases of rising and falling estrogen

OBJECTIVE

To investigate the association between urinary hormone levels and migraine, with particular reference to rising and falling levels of estrogen across the menstrual cycle in women with menstrual and menstrually related migraine.

METHODS

Women with regular menstrual cycles, who were not using hormonal contraception or treatments and who experienced between one and four migraine attacks per month, one of which regularly occurred on or between days 1 +/- 2 of menstruation, were studied for three cycles. Women used a fertility monitor to identify ovulation, conducting a test each day as requested by the monitor, using a sample of early morning urine. Urine samples were collected daily for assay of estrone-3-glucuronide, pregnanediol 3-glucuronide, follicle-stimulating hormone, and luteinizing hormone. All women kept a daily migraine diary and continued their usual treatment for migraine.

RESULTS

Of 40 women recruited, data from 38 women were available for analysis. Compared with the expected number of attacks, there was a significantly higher number of migraine attacks during the late luteal/early follicular phase of falling estrogen and lower number of attacks during rising phases of estrogen.

CONCLUSION

These findings confirm a relationship between migraine and changing levels of estrogen, supporting the hypothesis of perimenstrual but not postovulatory estrogen "withdrawal" migraine. In addition, rising levels of estrogen appear to offer some protection against migraine.

Prevention of menstrual attacks of migraine: A double-blind placebo-controlled crossover study

OBJECTIVE

To assess the effect of perimenstrual estradiol supplements on menstrual attacks of migraine associated with estrogen withdrawal.

METHODS

Women with regular menstrual cycles and menstrual migraine or menstrually related migraine completed an initial three-cycle assessment confirming eligibility for a six-cycle crossover study using estradiol or placebo to prevent menstrual attacks of migraine. Women collected early morning samples of urine daily for laboratory assay and used a fertility monitor to identify peak fertility associated with ovulation. Estradiol gel or placebo was first applied on the tenth day following the first day of peak fertility and continued daily until, and including, the second full day of menstruation. Women kept a daily migraine diary and continued their usual treatment for migraine. The main outcome was the number of days during gel use on which a migraine occurred.

RESULTS

Data from 35 women were available for a paired analysis. Percutaneous estradiol was associated with a 22% reduction in migraine days (RR 0.78, 95% CI 0.62 to 0.99, p = 0.04); these migraines were less severe and less likely to be associated with nausea. This was, however, followed by a 40% increase in migraine in the 5 days following estradiol vs placebo (RR 1.40, 95% CI 1.03 to 1.92, p = 0.03).

CONCLUSION

Although perimenstrual percutaneous estradiol showed benefit during treatment, this was offset by deferred estrogen withdrawal, triggering post-dosing migraine immediately after the gel was stopped. Further work could assess if this could be avoided by extending the duration of treatment with estradiol.